In simple ways, it is a kind of marketing their product. They offer selected no of coins to the first 100/50 members who apply for the Airdrop. In order to participate you just have to fill up a joining form which needs little informations like profile link, profile no etc. In some cases they will ask you to retreat their tweets/share their posts in Facebook etc.
Thanks.
I finally found a clue to do these things.
The Facebook and Twitter is a must, as well as telegram.
I registered a telegram today, in order to get the coins.
For me, this is a whole new world, which is so funny.